Electroencephalographic techniques, especially event-related electro- encephalographic potentials (ERP), have been used to examine the CNS functioning of individuals at low and high risk for drug dependence. The proposed study will employ these techniques in an examination of 300 non- drug dependent teenagers (aged 16-18) varying in their risk. Three risk factors will be investigated: 1) gender, 2) a family history of either opiate or alcohol dependence, and 3) a personal history of antisocial personality (ASP) characteristics. The ERP battery will include three sets of tasks which putatively challenge frontal brain function. One set of tasks will require rapid changes in strategy, planning, and/or cognitive set. The second task set will manipulate the complexity, speed, or timing of the required motor response. The third will provide measures of ERP activity during the anticipation of avoidable stressors. A fourth task set will evaluate EEG activity at rest and ERPs during "nonfrontal" tasks. The proposed study will evaluate the hypothesis that subjects at high putative risk for drug dependence (i.e. those with ASP disorder, or a family history of opiate dependence or alcohol dependence) exhibit signs of impaired functioning on tests of cognitive flexibility and motor regulation. In contrast, high risk FH+ or ASP+ subjects are hypothesized to function better than their low risk counterparts on tests of stress avoidance. The validity of these hypotheses will also be evaluated using a battery of more traditional neuropsychological tests.